Conductance of non-ballistic point contacts in hybrid systems "normal metal/superconductor" Cu/Mo-C and Cu/LaOFFeAs

TL;DR

This paper investigates the shape of Andreev conductance curves in non-ballistic NS heterosystems, highlighting the role of impurity scattering and comparing ballistic and non-ballistic regimes, including exotic superconductors like Mo-C and LaOFFeAs.

Contribution

It extends the analysis of conductance behavior to non-ballistic regimes in NS contacts with exotic superconductors, providing criteria to distinguish transport regimes.

Findings

Impurity scattering doubles the scattering cross section affecting conductance curves.

Criteria are developed to differentiate ballistic and non-ballistic transport regimes.

Analysis includes non-ballistic transport in contacts with Mo-C and LaOFFeAs superconductors.

Abstract

We consider the shape of the curves of "Andreev" conductance of non-ballistic point contact NS heterosystems depending on the bias voltage at the contact. The obtained shape of those curves is caused by the contribution from the mechanism of coherent scattering by impurities which doubles the scattering cross section. The behavior of generalized and differential conductance is compared for ballistic and non-ballistic transport regimes. The criteria are considered allowing one to discriminate between those regimes with the corresponding conduction curves similar in appearance. The analysis is extended to the case of non-ballistic transport in NS point contacts with exotic superconductors, molybdenum carbide Mo-C and oxypnictide La[O$_{1-x}$F$_{x}$]FeAs from a group of iron-based superconductors.